Typically, you will act as the Trustee of your own revocable living trust. This is primarily the case where the purpose of your trust is to plan for possible future incapacity or to avoid probate at the time of your death. For most purposes, you will want to remain in control for as long as possible, and serving as Trustee of your own trust is one way to accomplish this.
In fact, aside from re-titling your assets in the name of your trust, generally once your revocable living trust is established, you should see no practical change in the way you live your life. Yes, you are the Trustee, but on a day-to-day basis, you will continue going about your life without any substantive change to how you handle the management of your assets.
If a client is suffering from a condition that necessitates the help of another person to manage their assets, it may be worth considering bringing on a Co-Trustee or being replaced as the Trustee for the purpose of assisting the client with his financial affairs. In this particular case, the Trustor generally retains ultimate control and has the power to remove the Trustee, if necessary.